[Radioimmunotargeting: diagnosis and therapeutic use]

Monoclonal antibodies labeled with a radionuclide make feasible the in vivo radioimmunotargeting of tumor cells. This targeting could be performed for diagnosis, using gamma emitters, or for therapeutic purpose when antibodies are labeled with beta- and in the future alpha-emitters. Diagnosis applications (tumor detection and caracterization), i.e. immunoscintigraphy, have been widely investigated during 20 last years. This technic appeared quite interesting, complementary of morphological imaging, and clinically useful, but difficult on a practical point of view because of several pharmacological and immunological limitations. For these reasons, despite several consequent improvements (especially two-steps or pre-targeting methods), immunoscintigraphy is currently not widely used; furthermore, other scintigraphic methods, mainly positron emission tomography with 18F-fluorodeoxyglucose, are efficient and easier to perform. On the other hand, knowledge of the biodistribution of radiolabeled antibodies allows the development of their therapeutic use, i.e. radioimmunotherapy, which represents a new method of cancer treatment. Radioimmunotherapy has several particular radiobiological and dosimetric aspects, which remain widely under investigation. Understanding of these aspects, together with a better delineation of the indications, allow to be really optimist concerning this new way of cancer treatment, as shown by clinical results that have been obtained in non Hodgkin's lymphoma. Radiolabeled immunoconjugates appears as a growing field in nuclear medicine, which sustains numerous preclinical and clinical studies.